Spray the bottom and sides of a 6-quart oval slow cooking lightly with cooking spray.
Whisk together the chicken broth, whipping cream, cream cheese, garlic salt and pepper. Add the grits and 2 cups shredded cheese. Mix well.
Pour into the slow cooker, stir to evenly distribute the grits.
Cover and cook on low for 4-6 hours, stopping to stir periodically (Once after cooking for 2 hours then every hour or so thereafter, if possible) Cook until the grits are tender.
Uncover and stir-in butter. Mix until melted. Sprinkle the remaining cheese on top.
Let stand uncovered for 10 minutes prior to serving. Grits will thicken further as they cool.